I am the developer behind the new default theme, and I can assure you that the changes were in no way biased towards the community theme I had made previously. In fact it was the exact opposite.
The changes to the default theme are designed to make theme development easier and reduce maintenance work. We wanted to create a foundation that will reduce the chances that themes break in future updates to Obsidian. We also introduced the new theme versioning system to further improve the experience for users on older versions of Obsidian.
I understand how you feel, I’ve been there too. The decision to make big changes to the app is not made lightly because we know it creates work for the community. This is why we are giving community developers plenty of time to update before 0.16 is released publicly.
Once you have a chance to check out the 0.16.0 Theme Migration Guide I think you will find the new system of variables very convenient and it will speed up development for you.